1. Field of the Invention
The present invention relates to a photocurable resin composition for paints, adhesives, ink or the like, which is cured by light irradiation, and in particular, for rigid plastics such as polycarbonate, PET, and ABS resins having poor adhesive property.
2. Description of the Related Art
In resent years, plastic materials have been used widely in the field of electronic information materials. For example, polycarbonate, which is a rigid plastic, has been used frequently as a material for a cellular phone or an optical disk. Similarly, a PET resin has been used as a material for an optical film, and an ABS resin has been used as a material for the housing of home information appliances. In the processes for their productization, there are processes of adhering, coating, and printing by photocuring such rigid plastics. However, these materials have poor adhesive property. Meanwhile, the materials for paints, adhesives, ink and the like requires high adhesiveness to a resin matrix.
One method of providing high adhesive property, there has been known an effective method of decreasing residual stress generated in the adhesive interface by low curing shrinkage when curing the resin matrix. As a method of achieving the low curing shrinkage, a curing system using cationic ring-opening photopolymerization of cyclic ether such as an epoxy resin or an oxetane resin having low curing shrinkage has been proposed from a conventional curing system using additive polymerization by radical photopolymerization using an acrylic monomer and the like. However, the curing system using cationic ring-opening photopolymerization had difficulties in incorporating a functional group capable of interacting with rigid plastics to be adhered, thus the adhesive property was not given sufficiently.
Therefore, a comb polymer as an effective ingredient, which an anchor as a pigment dispersing agent is a base and which is in liquid state at room temperature, is added to a cationic ring-opening polymerization system containing an epoxy compound, an oxetane compound, a cationic photopolymerization initiator, a pigment as a coloring agent and a pigment dispersing agent in an attempt to exhibit adhesive property with a body to be adhered, thus sufficient adhesive property is exhibited (for example, see Japanese Unexamined Patent Application Publication No. 2003-212965). However, since this system contains basic materials which may act as a retarder (reaction inhibitor) in cationic ring-opening photopolymerization reaction, it has a drawback in that a sufficient curing rate, necessary for productivity, is not exhibited.